Field of Invention
The present invention relates to a high-side power device and a manufacturing method thereof; particularly, it relates to such a high-side power device having a reduced conduction resistance, and a manufacturing method thereof.
Description of Related Art
FIG. 1A shows a schematic diagram of a typical switching regulator 10. The switching regulator 10 has a high-side switch UG and a low-side switch LG as shown in the figure. A high-side gate driver circuit 13 and a lower gate driver 14 drive the high-side switch UG and the low-side switch LG respectively. A control circuit 11 controls the high-side gate driver circuit 13 (through a level shifter circuit 12) and the lower gate driver circuit 14. The level shifter circuit 12 is required when the input voltage Vin is a relatively high voltage, such as 400V; in this case, the level shifter circuit 12 provides the required signal level to the high-side gate driver circuit 13 so as to properly drive the high-side switch UG. Although the voltage drops between the operation terminals of the high-side switch UG, such as its source, drain, and gate, are not high relatively to the input voltage Vin, the high-side switch UG is still required to withstand a high voltage drop between the input voltage Vin and the ground level GND, because the high-side switch UG and the low-side switch LG are typically formed in a same substrate, and the substrate is usually electrically connected to the ground level GND.
FIG. 1B shows a schematic diagram of a cross-section view of a prior art high-side power device 100, for use as the high-side switch UG. As shown in FIG. 1B, the high-side power device 100 includes a substrate 101, an isolation oxide region 103, a high voltage well 105, a body region 106, a source 108, a drain 109, and a gate 111. The high voltage well 105 has an N-type conductive type and is formed in the substrate 101 which has a P-type conductive type. The isolation oxide region 103 is a local oxidation of silicon (LOCOS) structure, which defines an operation region 103a as a major active region of the high-side power device 100. The operation region 103a is shown in FIG. 1B as a region defined by two arrows. When the high-side power device 100 is used as the high-side switch UG, the substrate 101 of the high-side power device 100 is electrically connected to the ground level GND, and the high voltage well 102 is at a relatively high electric level; in a conduction operation, the high voltage well 102 in the operation region 103a is completely depleted, and therefore the conduction resistance is high, restricting the operation speed and operation performance of the high-side power device 100.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a high-side power device having a reduced conduction resistance, and a manufacturing method thereof.